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Acid drainage potential from coal mine wastes: environmental assessment through static and kinetic tests
Banerjee, D.
Abstract
The present study involved the assessment of
potential generation of acid drainage from a coal mining
area in India. Laboratory-based static and kinetic tests on
overburden samples were conducted. Results of the static
tests using acid base accounting indicate that all samples
may be acid generators, and their generation capacity
varied between likely, possible and low. To verify the acid
generation potentiality of those samples showing a high
acid drainage production in the static test, the kinetic test,
using humidity cell, was conducted for a period of
15 weeks. The samples were leached with simulated rain
water to mimic the chemical weathering under controlled
laboratory conditions and imitate actual mine site leaching.
Data obtained from chemical analysis of collected leachate
were used to estimate production and reaction rates of acid
generation and neutralizing capacity. Based on the kinetic
test, it can be concluded that presently the neutralizing
capacity of the samples is better than the oxidation capacity
(acid generation). But due to the high weathering rate of
carbonates, as reflected by the simulated leaching test, the
neutralizing materials (carbonates) will eventually be
exhausted earlier (since they showed dissolution rate) than
the acid generation species (sulfates). Thus, acid drainage
production is predicted from that point of time, when the
neutralizing capacity has been exhausted for these mine
sites.
Keywords
Acid base accounting; Humidity cell; Leaching kinetic; Oxidation–neutralization; Weathering rate
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